The broad implementation of a catalytic convertors adapted to manage and promote reaction of polluting chemical species exhausted by internal combustion engines has been very effective in reducing the extent of pollution attributable to automobiles and trucks. The effectiveness of the catalyst materials used depends on their operating temperature and has been optimized to enable peak or near-peak convertor performance when the engine is at its normal engine operating temperature. At lower catalytic convertor temperatures, even temperatures not significantly lower than those developed under normal engine operating temperatures, the ability of a catalyst to suitably promote exhaust gas reactions for control of pollutants is dramatically reduced.
Such reduced catalytic convertor temperatures are commonly encountered during the heat-up of an engine from a cold-start from ambient temperature, about 25° C. or so. Catalyst heat-up occurs much more rapidly than engine heat-up but it can still take about 100 seconds for a catalytic convertor to reach its effective operating temperature, commonly described as its light-off temperature. During this period little or no exhaust gas pollutant reduction occurs and an appreciable proportion of the pollutants emitted by the vehicle in a typical urban driving are emitted during this catalyst warm-up period.
There is therefore interest in reducing the duration of this catalyst warm-up period.